Mask relief valve for oxygen breathing systems



Nov. 21, 1950 s. R. oLDHAM ETAL 2,530,536

MASK RELIEF VALVE FOR OXYGEN BREATHING SYSTEMS Filed April l0, 1945 INVENToRs SAMUEL R.o| DHAM w|| GoT J. JAcoBssoN JAMES A. HOFFMAN ATTO RN EY Patented Nov. 21, 1950 UNITED STATES PATENT OFFICE MASK RELIEF VALVE FOB OXYGEN l BREATHING SYSTEMS Application April 10, 1945, Serial No. 587,538

4 Claims. l

'I'his invention relates to mask relief valves for oxygen breathing systems, in which oxygen is supplied to a face mask worn by a person, and more particularly to relief valves of this character for systems adapted to operate under positive pressure, in which the pressure supplied to the mask may vary as much as one-half pound per square inch, depending primarily upon the altitude or secondarily upon other conditions under which the breathing oxygen is supplied.

When 'a positive pressure oxygen breathing system is employed, it is necessary to maintain the positive pressure in the mask, in order to insure a continuous supply of oxygen to the person wearing the mask. At the same time it is necessary to permit the gas to be expelled from the mask at a slight increase in pressure, corresponding to exhalation in breathing under ordinary conditions. A further reason for the pressure differential is to prevent spilling or continuous leakage of oxygen to the atmosphere outside the mask. The increase in pressure which permits such expulsion should be kept to a minimum, so as not to require excessive eiort on the part of the person wearing the mask in exhaling.

The main object of the present invention is to provide a simple and effective mask relief valve for oxygen breathing systems of this character, which is supersensitive so as to be adapted to operate under a small pressure differential.

For aircraft use, at higher altitudes lower temperatures are encountered, as low as minus '70 F., and also the aircraft may take ofi' or land in tropic or desert conditions in which the temperature may be as high as plus 150 F. For these reasons it is another object of the present invention to provide a relief valve which will not freezeup at the low temperatures of high altitudes, and which will not be damaged by tropic or desert temperatures of take-ofi or landing.

In this reliefl valve the operating pressure is applied directly under a spring loaded diaphragm seated directly on a small radius nozzle located in the pressure chamber. The nozzle outlet connects directly. with Athe atmosphere. The diaphragm is made of thin anode rubber or other suitable material to provide flexibility for the pressure and over temperature range required. The diaphragm plate is centrally moulded, cemented or otherwise secured to the back of the diaphragm leaving the rim or margin free. The diaphragm is preferably formed with an annular bulge in the pressure direction between the diaphragm plate and the inside body edge to improve iiexing, and to allow sufficient freedom of motion for self-alignment with the nozzle edge for proper sealing. To the outer edge of the diaphragm is moulded or otherwise secured a stiffening or sealing ring of suitable material such as rubber or synthetic rubber. When the cap is secured to the body with clamping screws, the diaphragm is locked and sealed in place.

Other objects and features of novelty will be apparent as the following description proceeds, reference being had to the accompanying drawings, in which:

Fig. l is a cross section through an oxygen breathing mask relief valve according to the preferred embodiment of the present invention;

Fig. 2 is a similar view showing a modified form; and

held to a certain loading against a shoulder in the cap.

The valve has a relatively fiat shell comprising a body IIJ and a cap I2, between which is clamped a diaphragm I4 preferably of thin anodic rubber, or other material of sufficient flexibility for operation under the temperature range hereinbefore stated. The body I 0 is a flat circular disc, having a central inwardly directed annular flange forming a nozzle I 5, and an outer rim I6 against which the diaphragm is clamped. Between the nozzle I5 and the rim I6 is an annular chamber C, which communicates with the interior of the breathing mask through an inlet I 1.

The diaphragm I4 is clamped between the rim I 6 and the cap I2, a suitable stiening and packing ring I9 of rub-ber or the like, preferably integral with the outer margin of the diaphragm, being provided to insure sealing. A diaphragm plate 20 is centrally molded, cemented or otherwise secured to the back of the diaphragm opposite the nozzle I5. The diaphragm is provided with an annular bulge 2| in the pressure direction between the diaphragm plate and the outer edge of the diaphragm, to improve flexing and to allow sufficient freedom of motion to permit self-alignment of the face of the diaphragm with its seating surface or edge on the nozzle I5 and effect proper sealing. Thus the diaphragm floats upon its exible margin. The thin stock rubber of the diaphragm itself seals the seat of the nczzle.

The cap l2 has a hollow central annular boss provided with a large central aperture 23 for free venting of the spring loaded side of the diaphragm. The inner side of the boss has an annular shoulder 24, and the loading spring- 25 is interposed between this shoulder and the diaphragm plate 20, a circular centering and reenforcing plate 26 being cemented to the diaphragm plate. The spring 25 is a large diameter coil of small diameter Wire, accurately constructed to give the speciiic pressure required.

The diaphragm plate 2U and the reinforcing plate 2B are provided with a central aperture or bleed vent 21, to discharge any air which might otherwise be trapped 4behind the diaphragm I4. Because of the practical impossibility of providing an absolutely smooth coating of cement, no cement is provided directly under the nozzle I5, which accordingly presses the diaphragm directly against the plate 20. However, the cement is applied between the diaphragm I4 and the plate 20 over a central area within the contines of the nozzle l5. Thus the loose annular area of the diaphragm in back of the nozzle I may permit the entrance of air, particularly in View of the pumping action of the diaphragm, and the vent hole 21 prevents this air from forming bubbles under the diaphragm.

The casing I0 is provided with a drain aperture 29 communicating with the bottom of the chamber C, and closed by a drain valve 3U. The valve 30 is held closed by a spring 3| and is adapted to be opened by depressing a button 32 pressing against a pin 33 engaging the spring 3i. This drain valve permits the breather to discharge any moisture accumulated from the exhaled gases.

In operation, when the breather exhales and the pressure in the mask exceeds the predetermined relief pressure, this pressure within the chamber C acts on the annular area of the diaphragm outside of the nozzle, and overcomes the spring to force the diaphragm away from the nozzle, permitting exhaled gases to escape through the nozzle to the atmosphere. As soon as exhalation is completed, the pressure in chamber C drops to the positive pressure of the oxygen supplied to the interior of the mask, and the spring returns the diaphragm to position closing the nozzle I5, thus preventing the escape of oxygen until another exhalation is begun.

In the valve shown in Figs. 2 and 3, means are provided for adjusting the relief pressure of the valve. A lever spring loading mechanism is employed, having an adjustable compression spring. The differential pressure between open and closed position is about l to 2 centimeters of water. For light-weight construction a phenolformaldehyde resin or other suitable light-weight material is used for molding the body, the cap, and the inlet connections. The nozzle is made of methylmethacrylate resin or other material for ease in manufacture to minimize tackiness of rubber against the nozzle, and to prevent freeze-up. This material permits accurate construction whether by machining or molding, so that the nozzle edge can be made Very accurately.

In the valve shown in Figs. 2 and 3, the cap 3B is a at circular disc, which has secured thereto a pair of ears 31 supporting a pin 38 which forms the fulcrum of a lever 39 extending laterally inwardly and having a pin 4l) secured thereto. The pin 40 extends through a central hole 4l in the cap 36, which forms a means for venting the space in back of the valve, and the pin 40 has a rounded end which engages the vent hole 21 in the plate 26 which here acts as a reenforcing plate. The end of the pin 4D does not fit the hole 21 accurately enough to seal the same, and there is sufficient leakage for the bleed purposes thereof.

Surrounding the ears 31 and fulcrum 38 is a casing 42 which houses a coil compression spring 43. The inner end of the springy 43 engages a bearing member 44 having a. spherical seat which enters a depression 45 in the lever 39 adjacent its fulcrum 38. The outer end of the spring 43 engages a bearingl member 46 which*` forms a seat for the inner end of an adjusting screw 41 thread- `ed in the outer end of the casing 42. The remaining parts are identical with those of Fig. 1.

The lever arrangement thus provided is such that the lever arm acted upon by the exhalatlon pressure is many times the length of the lever of the lever arm acted upon by the spring pressure, so as to multiply the eect of the exhaust pressure, and greatly reduce the effect of the spring pressure. With this arrangement, great accuracy of the spring characteristics is not so important. Accordingly, this permits the use of less expensive springs, because stronger springs of fairly accurate characteristics are less expensive and require less space than a corresponding accurate spring of the weaker type shown in Fig. 1. The general operation of this Valve is the same as described for Fig. l.

Having thus described our invention, we claim:

1. A relief valve for oxygen breathing masks comprising a relatively ilat annular body having an inlet opening and an outlet opening for exhaust to the atmosphere, said openings being of the same diameter, one concentric with 'said annular body and having a rim forming a valve seat, the other being eccentric to said annular body, a relatively iiat circular cover for said body, a valve comprising a thin rubber diaphragm clamped between said body and cover and directly engaging said seat, a backing plate extending over the greater part of the area of said diaphragm, a circular reinforcing and centering plate secured to the side of said backing plate away from said diaphragm, said plates having registering central apertures forming a bleed vent therethrough to discharge any air trapped behind the diaphragm; a spring for urging said backing plate toward said Valve seat to contact said rubber disaphragm with said seat in closing position, said spring being constructed and arranged to permit opening of said valve in response to a pressure of a few centimeters of water, and said cover having means for venting the space in back of said valve to prevent pressure resistance to opening of said valve.

2. A relief valve for oxygen breathing masks as claimed in claim 1, in which a lever mechanism is pivotally mounted at one end on said cover and having its movable end engaging the center of said valve, said spring having one end engagng said lever mechanism for closing said valve, said cover having a housing for the other end of said spring, a bearing member within said housing and engaging said spring, and a screw threaded means cooperating with said housing to move said bearing member for adjusting the compression of said spring.

3. A relief valve for oxygen breathing masks as claimed in claim 1, in which said cover has a hollow central annular boss with an internal annular shoulder, and a large diameter coil loading spring of small diameter wire enclosed within said boss and engaging said shoulder and bear- 5 ing against said valve for urging said valve against said seat to close said outlet.

4. A relief valve for oxygen breathing masks as claimed in claim l, in which a lever is pivoted outside of said cover, said spring engaging said 5 lever, and a pin on said lever passing through an aperture in said cover to engage said valve for urging it against said seat to close said outlet.

SAMUEL R. OLDHAM. WILGOT J. JACOBSSON. 10 JAMES A. HOFFMAN.

REFERENCES CITED The following references are of record in the 1I le of this patent:

Number Number Germany Nov. 19, 1920 

